JAVA Interview Question

What is Collection API ?
The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vectors, arrays, and hashtables if effectively replaces.
Example of classes: HashSet, HashMap, ArrayList, LinkedList, TreeSet and TreeMap.
Example of interfaces: Collection, Set, List and Map.
Is Iterator a Class or Interface? What is its use?
Answer: Iterator is an interface which is used to step through the elements of a Collection.
What is similarities/difference between an Abstract class and Interface?
Differences are as follows:
Interfaces provide a form of multiple inheritance. A class can extend only one other class. Interfaces are limited to public methods and constants with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc.
A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class. Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.
Similarities:

Neither Abstract classes or Interface can be instantiated.
Java Interview Questions - How to define an Abstract class?
A class containing abstract method is called Abstract class. An Abstract class can't be instantiated.
Example of Abstract class:
abstract class testAbstractClass {
protected String myString;
public String getMyString() {
return myString;
}
public abstract string anyAbstractFunction();
}

Architecture of the Servlet Package

The javax.servlet package provides a set of interfaces and classes for writing servlets.

These classes and interfaces are normally found in 'Enterprise Edition' versions of the Java SDK. They are also included within TJI's ide.jar so that servlets can be developed by those without an EE SDK.

The architecture of the servlet package is described below.

How to Design Online Quiz Application

In this section, we are going to implement of Online quiz application using of JSP.
  
Step 1: Create Question and answer insert form (questForm.jsp) .

In this step first of all create quiz question and answer form using with JSP or JDBC database.

How to retrieve data from database, using servlet or a jsp?

Basics of Database Connectivity 
In java we have been provided with some classes and APIs with which we can make use of the database as we like. Database plays as very important role in the programming because we have to store the values somewhere in the back- end. So, we should know how we can manipulate the data in the database with the help of java,  instead of going to database for a manipulation. We have many database provided like Oracle, MySQL etc. We are using MySQL for developing this application. 
In this section, you will learn how to connect the MySQL database with the Java file. Firstly, we need to establish a connection between MySQL and Java files with the help of MySQL driver .  Now we will make our  account in MySQL database so that we can get connected to the database. After establishing a connection  we can access or retrieve data form MySQL database. We are going to make a program on connecting to a MySQL database, after going through this program you will be able to establish a connection on your own PC

Java Aptitude Questions

What  is Java?
Java is an object-oriented programming language developed initially by James Gosling and colleagues at Sun Microsystems. The language, initially called Oak (named after the oak trees outside Gosling's office), was intended to replace C++, although the feature set better resembles that of Objective C. Java should not be confused with JavaScript, which shares only the name and a similar C-like syntax. Sun Microsystems currently maintains and updates Java regularly.